Synthetic doors are now common place as a replacement for the traditional wooden doors in residential and commercial buildings. Such synthetic doors are formed with resin sheets reinforced with fiber glass (in the art referred to as skins) attached to opposite sides of a rectangular frame with resulting cavity between the skins filled with a plastic foam. Doors so constructed do not warp, are not subject to insect infestation and are resistant to the elements. Moreover such doors can include wood graining on the outer surfaces of the skins, and also paneling formed in the skins, which gives these doors the appearance of natural wood fabricated products.
Molded skins for making doors of the type described are disclosed in U.S. Pat. No. 3,950,894 issued to DiMaio and in U.S. Pat. No. 4,550,540 issued to Thorn. These skins are typically formed using mixtures, having by weight 12% to 15% polyester resin, 5% to 15% polystyrene, 40% to 50% calcium carbonate and 15% to 25% chopped fiberglass. Such mixtures are layered in a compression molding machine and subjected to pressures from 600 to 1,500 psi for a cure cycle from 60 to 200 seconds to form rigid skins. The mixture described is one of those known as xe2x80x98sheet molding compoundsxe2x80x99 [SMCs]. A general description of the sheet molding process is found in an article entitled xe2x80x9cCompression Moldingxe2x80x9d by N. D. Simons in Modern Plastics Encyclopedia, Vol. 54 No. 0AS (1977-78).
Skins formed from SMC processes for doors can have thickness of from about 0.05 inches to about 0.20 inches, depending on the door application.
In the market place manufacturers of such doors face serious competition and any small decreases in the costs can often provided a manufacturer with a market advantage.
As previously noted such skins are affixed to opposite sides of a rectangular frame and core (cavity) enclosed by the frame and skins is filled with a plastic foam to complete the door, see for example the wooden frame in U.S. Patent Letters patent issued U.S. Pat. No. 4,550,540 issued to Thorn. A rigid urethane foam having a density of 0.8 pounds per cubic foot to 3.5 pounds per cubic foot is suitable for the core of such doors.
Wooden frames, the stiles and rails of the door, as shown in Thorn, are costly components. This invention relates to an edge insert incorporated into thin wooded stiles to increase the strength of the stiles and to stiffen them thereby improving both the door strength and the ease of fabrication while using thinner wooden stiles. In addition the insert provides finished vertical edges in the completed door without added costs
This innovative edge insert is mechanically joined to the stiles to form a reinforced stile on both left side and right side of the molded door thereby providing an improved door. In addition the edge insert can be manufactured to deliver a host of edge configurations for the door such as wood graining, as well as providing a finished edge for any wooden element used the stiles.
An advantage is that the invention allows the smaller cross sectional configurations for the wooden stiles with out loss of strength or problems in production with an accompanying cost saving.
In the past formed extrusions have been employed as the stiles and rails of such doors, but it has been found that such extruded parts are too expensive to be competitive.
A synthetic door composed of two molded skins attached to a frame composed of thin wooden stiles and rails to which the skins are adhered, with the cavity between skins filled with a plastic foam wherein the stiles have a width of lesss than 1.5 inches the improvement comprising an insert mechanically joined to each stile along their entire length, each said inserts having a channel means operable to interlock with its associated stile and forming a finished outer edge on the stile. The insert is typically formed of a foamed polyvinyl chloride [PVC] extrusion.
In addition the insert can be employed to form an interlocking frame by extending the insert beyond the ends of the stiles and milling the ends of the rails so that they interlock with the channel means of the insert.